If the demand for the game on other systems was high enough to them to go back on it being an exclusive title, I'm guessing they're really not going to care about these letters you're proposing.
They saw the dollar signs in selling to a much bigger install base. even if it does flop on the Wii U they're still going to sell more to PS3 and 360 owners, much more than they probably would just selling it on the Wii U. So in the end they're still increasing sales.
A word to the wise ain't necessary - it's the stupid ones that need the advice